1. Field of the Invention
The present invention relates to new crystalline molecular sieve CIT-6, a method for preparing CIT-6 using a tetraethylammonium cation templating agent, a method of using CIT-6 as a precursor for making other crystalline molecular sieves, and processes employing CIT-6 as a catalyst.
2. State of the Art
Because of their unique sieving characteristics, as well as their catalytic properties, crystalline molecular sieves are especially useful in applications such as hydrocarbon conversion, gas drying and separation. Although many different crystalline molecular sieves have been disclosed, there is a continuing need for new molecular sieves with desirable properties for gas separation and drying, hydrocarbon and chemical conversions, and other applications. New molecular sieves may contain novel internal pore architectures, providing enhanced selectivities in these processes.
The present invention is directed to a crystalline molecular sieve with unique properties, referred to herein as xe2x80x9cmolecular sieve CIT-6xe2x80x9d or simply xe2x80x9cCIT-6xe2x80x9d. When the CIT-6 contains a metal (or non-silicon) oxide, such as aluminum oxide, boron oxide, titanium oxide or iron oxide, it is referred to as xe2x80x9ccatalytically activexe2x80x9d CIT-6.
The CIT-6 can be made in two forms. The first contains silicon oxide, zinc oxide and optional metal (or non-silicon) oxides (such as aluminum oxide), wherein the zinc is in the crystal framework of the CIT-6. This form of CIT-6 is referred to herein as xe2x80x9cZn-CIT-6xe2x80x9d.
Another form of CIT-6 is where the molecular sieve is composed only of silicon oxide. This form of CIT-6 is referred to herein as xe2x80x9call-Si CIT-6xe2x80x9d.
Zn-CIT-6 and all-Si CIT-6 each have the topology of zeolite beta.
In accordance with this invention, there is provided a molecular sieve comprising an oxide of silicon and an oxide of zinc and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework.
The present invention further provides such a molecular sieve having the topology of zeolite beta, and having a composition, as synthesized and in the anhydrous state, in terms of mole ratios as follows:
wherein M is lithium or a mixture of lithium and another alkali metal, and Q comprises a tetraethylammonium cation, wherein the molecular sieve contains zinc in its crystal framework.
Also in accordance with this invention there is provided a molecular sieve comprising silicon oxide, zinc oxide, and an oxide selected from aluminum oxide, boron oxide, gallium oxide, iron oxide, titanium oxide, vanadium oxide, zirconium oxide, tin-oxide or mixtures thereof and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework.
The present invention also provides such a molecular sieve having the topology of zeolite beta, and having a composition, as synthesized and in the anhydrous state, in terms of mole ratios as follows:
wherein W is an oxide of aluminum, boron, gallium, vanadium, iron, titanium or mixtures thereof M is lithium or a mixture of lithium and another alkali metal and Q comprises a tetraethylammonium cation, wherein the molecular sieve contains zinc in its crystal framework.
Also provided in accordance with the present invention is a method of preparing a crystalline material comprising an oxide of silicon and an oxide of zinc and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework, said method comprising contacting in admixture under crystallization conditions sources of said oxides, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation.
The present invention also provides a method of preparing a crystalline material comprising an oxide of silicon, an oxide of zinc and an oxide selected from aluminum oxide, boron oxide, gallium oxide, vanadium oxide, iron oxide, titanium oxide or mixtures thereof and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework, said method comprising contacting in admixture under crystallization conditions sources of said oxides, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation.
Further provided by the present invention is a method of removing a tetraethylammonium organic template from the pores of a molecular sieve, said method comprising contacting the molecular sieve with acetic acid, or a mixture of acetic acid and pyridine at elevated temperature for a time sufficient to remove essentially all of the tetraethylammonium organic template from the molecular sieve. In a preferred embodiment, the molecular sieve has the topology of zeolite beta.
The present invention further provides a method of removing an organic template from the pores of a molecular sieve and at the same time removing zinc atoms from the framework of the molecular sieve, wherein the molecular sieve comprises an oxide of silicon, an oxide of zinc and, optionally an oxide selected from aluminum oxide, boron oxide, gallium oxide, vanadium oxide, iron oxide, titanium oxide or mixtures thereof and has the framework topology of zeolite beta, said method comprising contacting the molecular sieve with acetic acid or a mixture of acetic acid and pyridin at elevated temperature for a time sufficient to remove essentially all of the organic template and zinc from the molecular sieve. The present invention also provides the product of this method.
Also provided by the present invention is a method of making a crystalline material comprising (1) contacting in admixture under crystallization conditions a source of silicon oxide, a source of zinc oxide, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation until a crystalline material comprised of oxides of silicon and zinc and having the topology of zeolite beta is formed, (2) contacting the crystals with acetic acid or a mixture of acetic acid and pyridine at an elevated temperature of about 60xc2x0 C. or less for a time sufficient to remove essentially all of the organic template and zinc from the crystals, and (3) contacting the crystals with a solution containing a source of aluminum, boron, gallium, iron, vanadium, titanium, zirconium, tin or mixtures thereof. The present invention also provides the product of this method.
This invention also provides a crystalline molecular sieve having the topology of zeolite beta, a crystal size of less than one micron and a water adsorption capacity of less than 0.05 g/g of molecular sieve.
Further provided by the present invention is a crystalline silicate molecular sieve having the topology of zeolite beta, a crystal size of less than one micron and a water adsorption capacity of less than 0.05 g/g of molecular sieve.
In addition, the present invention provides a method of preparing a crystalline material having the topology of zeolite beta comprising impregnating a silica-containing mesoporous material with an aqueous solution comprising tetraethylammonium cation in an amount sufficient to form a crystalline product having the topology of zeolite beta, and wherein the water to mesoporous material molar ratio is from about 0.5 to about 2, and subjecting the impregnated mesoporous material to crystallizing conditions of heat and pressure for a time sufficient to form crystals of a material having the topology of zeolite beta.
The present invention additionally provides a process for converting hydrocarbons comprising contacting a hydrocarbonaceous feed at hydrocarbon converting conditions with a catalyst comprising a catalytically active molecular sieve comprising silicon oxide, zinc oxide, and an oxide selected from aluminum oxide, boron oxide, gallium oxide, iron oxide, zirconium oxide, tin oxide or mixture thereof and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework. The molecular sieve may be predominantly in the hydrogen form, partially acidic or substantially free of acidity, depending on the process.
Further provided by the present invention is a hydrocracking process comprising contacting a hydrocarbon feedstock under hydrocracking conditions with a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form.
This invention also includes a dewaxing process comprising contacting a hydrocarbon feedstock under dewaxing conditions with a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form.
The present invention also includes a process for improving the viscosity index of a dewaxed product of waxy hydrocarbon feeds comprising contacting the waxy hydrocarbon feed under isomerization dewaxing conditions with a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form.
The present invention further includes a process for producing a C20+ lube oil from a C20+ olefin feed comprising isomerizing said olefin feed under isomerization conditions over a catalyst comprising at least one Group VIII metal and the catalytically active molecular sieve of this invention. The molecular sieve may be predominantly in the hydrogen form.
In accordance with this invention, there is also provided a process for catalytically dewaxing a hydrocarbon oil feedstock boiling above about 350xc2x0 F. and containing straight chain and slightly branched chain hydrocarbons comprising contacting said hydrocarbon oil feedstock in the presence of added hydrogen gas at a hydrogen pressure of about 15-3000 psi with a catalyst comprising at least one Group VIII metal and the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form. The catalyst may be a layered catalyst comprising a first layer comprising at least one Group VIII metal and the catalytically active molecular sieve of this invention, and a second layer comprising an aluminosilicate zeolite which is more shape selective than the catalytically active molecular sieve of said first layer.
Also included in the present invention is a process for preparing a lubricating oil which comprises hydrocracking in a hydrocracking zone a hydrocarbonaceous feedstock to obtain an effluent comprising a hydrocracked oil, and catalytically dewaxing said effluent comprising hydrocracked oil at a temperature of at least about 400xc2x0 F. and at a pressure of from about 15 psig to about 3000 psig in the presence of added hydrogen gas with a catalyst comprising at least one Group VIII metal and the catalytically active molecular sieve of this invention. The molecular sieve may be predominantly in the hydrogen form.
Further included in this invention is a process for isomerization dewaxing a raffinate comprising contacting said raffinate in the presence of added hydrogen with a catalyst comprising at least one Group VIII metal and the catalytically active molecular sieve of this invention. The raffinate may be bright stock, and the molecular sieve may be predominantly in the hydrogen form.
Also included in this invention is a process for increasing the octane of a hydrocarbon feedstock to produce a product having an increased aromatics content comprising contacting a hydrocarbonaceous feedstock which comprises normal and slightly branched hydrocarbons having a boiling range above about 40xc2x0 C. and less than about 200xc2x0 C., under aromatic conversion conditions with a catalyst comprising the catalytically active molecular sieve of this invention made substantially free of acidity by neutralizing said molecular sieve with a basic metal. Also provided in this invention is such a process wherein the molecular sieve contains a Group VIII metal component.
Also provided by the present invention is a catalytic cracking process comprising contacting a hydrocarbon feedstock in a reaction zone under catalytic cracking conditions in the absence of added hydrogen with a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form. Also included in this invention is such a catalytic cracking process wherein the catalyst additionally comprises a large pore crystalline cracking component.
Also provided by the present invention is a process for alkylating an aromatic hydrocarbon which comprises contacting under alkylation conditions at least a molar excess of an aromatic hydrocarbon with a C2 to C20 olefin under at least partial liquid phase conditions and in the presence of a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form. The olefin may be a C2 to C4 olefin, and the aromatic hydrocarbon and olefin may be present in a molar ratio of about 4:1 to about 20:1, respectively. The aromatic hydrocarbon may be selected from the group consisting of benzene, toluene, ethylbenzene, xylene, or mixtures thereof.
Further provided in accordance with this invention is a process for transalkylating an aromatic hydrocarbon which comprises contacting under transalkylating conditions an aromatic hydrocarbon with a polyalkyl aromatic hydrocarbon under at least partial liquid phase conditions and in the presence of a catalyst comprising the catalytically active molecular sieve of this invention, preferably predominantly in the hydrogen form. The aromatic hydrocarbon and the polyalkyl aromatic hydrocarbon may be present in a molar ratio of from about 1:1 to about 25:1, respectively. The aromatic hydrocarbon may be selected from the group consisting of benzene, toluene, ethylbenzene, xylene, or mixtures thereof, and the polyalkyl aromatic hydrocarbon may be a dialkylbenzene.
Further provided by this invention is a process to convert paraffins to aromatics which comprises contacting paraffins under conditions which cause paraffins to convert to aromatics with a catalyst comprising the catalytically active molecular sieve of this invention, said catalyst comprising gallium, zinc, or a compound of gallium or zinc.
In accordance with this invention there is also provided a process for isomerizing olefins comprising contacting said olefin under conditions which cause isomerization of the olefin with a catalyst comprising the catalytically active molecular sieve of this invention.
Further provided in accordance with this invention is a process for isomerizing an isomerization feed comprising an aromatic C8 stream of xylene isomers or mixtures of xylene isomers and ethylbenzene, wherein a more nearly equilibrium ratio of ortho-, meta- and para-xylenes is obtained, said process comprising contacting said feed under isomerization conditions with a catalyst comprising the catalytically active molecular sieve of this invention.
The present invention further provides a process for oligomerizing olefins comprising contacting an olefin feed under oligomerization conditions with a catalyst comprising the catalytically active molecular sieve of this invention.
This invention also provides a process for converting lower alcohols and other oxygenated hydrocarbons comprising contacting said lower alcohol or other oxygenated hydrocarbon with a catalyst comprising the catalytically active molecular sieve of this invention under conditions to produce liquid products.
Also provided by the present invention is an improved process for the reduction of oxides of nitrogen contained in a gas stream in the presence of oxygen wherein said process comprises contacting the gas with a molecular sieve, the improvement comprising using as the molecular sieve, the molecular sieve of this invention. The molecular sieve may contain a metal or metal ions (such as cobalt, copper or mixtures thereof) capable of catalyzing the reduction of the oxides of nitrogen, and may be conducted in the presence of a stoichiometric excess of oxygen. In a preferred embodiment, the gas stream is the exhaust stream of an internal combustion engine.
Further provided by the present invention is a method of removing liquid organic compounds from a mixture of liquid organic compounds and water, comprising contacting the mixture with an all-silica molecular sieve having the framework topology of zeolite beta, a crystal size less than one micron and a water adsorption capacity of less than 0.05 g/g of molecular sieve.
The present invention further provides a method of removing liquid organic compounds from a mixture of liquid organic compounds and water, comprising contacting the mixture with a molecular sieve comprising an oxide of silicon, an oxide of zinc and, optionally, an oxide selected from aluminum oxide, boron oxide, gallium oxide, iron oxide, vanadium oxide, titanium oxide, zirconium oxide, tin oxide and mixtures thereof, and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework.